The present invention relates to an exposure unit in an image recording apparatus, and more particularly to such unit in which light emitted from a light source is reflected at or transmitted through an original and the light directing from the original is irradiated onto an image recording medium such as photosensitive pressure sensitive recording medium.
An image recording medium is generally classified into a self-contained type recording medium and a transfer type recording medium. In the self-contained type recording medium, an encapsulated chromogenic material or dye precursor and a developer material are co-deposited on one surface of a single substrate as one layer or as two contiguous layers. The self-contained type is disclosed in U.S. Pat. No. 4,440,846.
In the transfer type recording medium, the developer material is coated on a separate substrate as a separate developer or copy sheet. The transfer type is disclosed in U.S. Pat. No. 4,399,209. More specifically, the transfer type image recording medium comprises a microcapsule sheet (first image recording medium) and a developer sheet (second image recording medium). The first image recording medium comprises a photosensitive pressure sensitive recording medium provided with microcapsules which encapsulate therein a first material (chromogenic material or dye precursor) having first and second phases dependent on light exposure. The second image recording medium comprises the developer medium provided with a second material (developer material) which provides an output image upon reaction with the first material.
A commonly assigned copending U.S. patent application Ser. No. 244,681 has been filed on Sept. 14, 1988 which discloses an image recording apparatus shown in FIG. 1. This apparatus employs the transfer type image recording medium comprising a photosensitive pressure sensitive recording medium 20 and a developer medium 21. The apparatus has a main frame 30 and an upper wall 30a, and an original stand cover 1 is mounted on the upper wall 30a. Below the cover 1, a transparent original stand glass 2 is provided. Between the original stand cover 1 and the original stand glass 2, an original (not shown) is interposed with its imaging surface facing down. The original stand glass 2 and the cover 1 are movable in a direction indicated by an arrow. A during exposure operation by a drive means (not shown). The upper wall 30a is formed with a slit 30b extending in a direction perpendicular to the moving direction of the original stand glass 2.
Within the main frame and below the original stand glass 2, there is provided an exposure unit including an optical system B. The optical system B is partitioned by a lamp housing 4. The lamp housing 4 is formed with a slit 14. The optical system B has a linear light source 3 for irradiating light to the imaging surface of the original. The light source 3 is adapted to impart linear light to the original surface through the linear slit 30b. Therefore, when the original is moved in the direction A upon movement of the cover 1 and the glass 2, a predetermined area of the original can undergo linear light irradiation for successively irradiating the entire imaging area of the original.
The optical system B also includes a reflection mirror 5 disposed beside the light source 3. The reflection mirror 5 is adapted to reflect partial light from the light source 3 toward the slit 30b, which partial light has not been directly oriented toward the slit 30b from the light source 3. The optical system B directs light reflected at or transmitted through the original toward an exposure zone E by a first reflector 6a and a second reflector 6b through a shutter 9, a lens 10 and a filter means 11. The first reflector 6a is adapted to reflect light from the the original toward the shutter 9. The shutter 9 allows the light to selectively pass therethrough for selectively directing the light toward the lens 10. The filter 11 is disposed immediately downstream of the lens with respect to optical path P. The filter means 11 is adapted to selectively transmit light having specific wavelength therethrough. More specifically, the filter means 11 includes at least three filter members for selectively passing therethrough each one of cyan, magenta and yellow lights. At one end portion of the main frame 30, the second reflector 6b is disposed for reflecting the thus directed light toward the exposure zone E through the slit 14.
Within the main frame 30, and below the lamp housing 4, a photosensitive sheet cartridge 13 is disposed in which the rolled photosensitive pressure sensitive sheet 20 is accomodated. The exposure zone E is defined at an upper surface area of the cartridge 13. A plurality of sheet feed rollers 13a are rotatably disposed around the sheet cartridge 13. These rollers 13a are adapted to transfer the photosensitive pressure sensitive sheet 20 in the cartridge 13 toward a pressure developing unit 15. In this case, the travelling speed of the photosensitive sheet 20 is synchronous with the moving speed of the original support glass 2, and therefore, when the sheet 20 passes through the exposure zone E, a latent image corresponding to the original image is formed on the sheet 20.
The pressure developing unit is positioned downstream of the exposure zone E, and below the unit 15 a developer sheet cassette 17 is disposed, in which cut developer sheets 21 are accomodated. Above the cassette 17 a sheet delivery roller 16 is provided for supplying each one of the developer sheets 21 toward the pressure developing unit 15. A sheet guide 16a is provided between the cassette 17 and the pressure developing unit 15 for guiding travel of the developer sheet 21.
Immediately upstream of the pressure developing unit, the developer sheet 21 is superposed with the photosensitive pressure sensitive recording medium 20 which carries the latent image. These sheets 20 and 21 are subjected to pressure developing operation at the unit 15, where the non-photo-cured microcapsules on the sheet 20 are ruptured by the pressure application, so that chromogenic materials are flowed from the ruptured microcapsules to react with the developer material, to thereby obtain a visible image on the developer sheet. The pressure developing unit 15 has a guide roller 15a so as to direct the sheets 20 and 21 downwardly. Details of the unit 15 are disclosed in a copending U.S. patent application Ser. No. 157,478 filed on Feb. 17, 1988.
A separation roller 15b is provided at a position immediately downstream of the pressure developing unit 15 for separating the photosensitive pressure sensitive sheet 20 from the developer sheet 21. Beside the separation roller 15b, a second guide roller 15c is provided for changing direction of the sheet 20. Further, at another upper side of the main frame 30, a take-up means 19 is provided for winding the photosensitive sheet 20 thereover.
At a downstream side of the guide roller 15b and above the cassette 17, a developer sheet guide roller 17a is disposed. Further, a thermal fixing unit 18 is disposed at a position downstream of the developer sheet guide roller 17a for obtaining glossy image on the developer sheet 21. The thus treated developer sheet is discharged out of the main frame through a discharge port 30c.
In such image recording apparatus, the amount of light irradiation from the light source is intended to be increased in order to increase exposure speed or to enhance exposure accuracy. However, if the amount of light irradiation exceeds a predetermined level, infrared rays are also increased, and the rays may thermally deteriorate the original. Therefore, high speed exposure or highly accurate exposure operation may not be conducted.
Further, since the elongated slit 30b is formed on the upper wall 30a of the main frame 30, foreign objects may enter into an interior space defined by the lamp housing 4. Therefore, components in the optical system may be contaminated with the foreign objects.